1. Field of the Invention
The present invention relates to a liquid ejection head, a liquid ejection apparatus and an image forming apparatus, and more particularly, to technology for forming supply restrictors and nozzles in a liquid ejection head.
2. Description of the Related Art
An inkjet type image forming apparatus has a print head in which a plurality of nozzles (ejection ports) are arranged in the form of a matrix, and it forms an image on a recording medium by ejecting ink droplets from the nozzles onto the recording medium. Furthermore, there are print heads which are assembled by layering together a plurality of plate members and bonding them by means of an adhesive, or the like. Inside a print head of this kind, ink supply ports (ink flow channels) are provided between pressure chambers connected to the nozzles, and a common liquid chamber which stores ink and supplies ink to the pressure chambers. Supply restrictors having a very fine hole diameter are provided in the ink supply ports or a portion thereof. The supply restrictors function as flow resistors for the liquid flowing through same, and they serve to reduce reflux of ink from the pressure chambers to the common liquid chamber, while stabilizing the ejection of ink from the nozzles.
In image forming apparatuses of this kind, in recent years, there have been demands for even higher image quality. In order to achieve high image quality, it is necessary to form all of the nozzles provided in the print head in a uniform fashion, while ensuring that there is little variation in same. If there are disparities in the nozzle diameter, nozzle positions, or the like, then variations will occur in the amount of ink ejected by the nozzles and in the ink ejection speed, and therefore, differences will appear in the sizes and landing positions of the dots formed on the recording medium, thus leading to reduced image quality. Therefore, technologies for processing the nozzles to a high degree of accuracy have been disclosed (see, for example, Japanese Patent Application Publication Nos. 10-76666, 5-330064, 10-291318 and 2000-218802).
Japanese Patent Application Publication No. 10-76666 discloses technology for forming nozzles by irradiating a laser beam onto a nozzle plate from both the ink input side and the ejection side.
Japanese Patent Application Publication No. 5-330064 discloses technology for forming nozzles by irradiating a broadening laser beam from outside the nozzle surface, onto nozzle forming positions (the nozzle surface) after assembling a print head.
Japanese Patent Application Publication No. 10-291318 discloses technology whereby a plurality of inversely tapered nozzles are processed simultaneously by irradiating light through a telecentric optical system while scanning a laser light source, after assembling a print head.
Japanese Patent Application Publication No. 2000-218802 discloses technology for simultaneously processing a plurality of inversely tapered nozzles by disposing a plurality of masks and a telecentric optical system between a laser light source and a print head, after assembly of the print head, and irradiating a plurality of laser beams corresponding to the mask images onto nozzle forming positions (the nozzle surface) in the print head.
However, in the above-described related arts, although technology for processing nozzles to a high degree of accuracy is proposed, no consideration is given to supply restrictors. Even if nozzles are processed to a high degree of accuracy, if the processing accuracy of the supply restrictors which are connected to the nozzles via the pressure chambers is low, then variations occur in the pressure loss of the supply restrictors. Accordingly, the ratio between the flow channel loss in the supply restrictors and the flow channel loss in the nozzles (pressure loss ratio) become uneven, and the pressure loss balance is not stabilized among the pressure chambers. Therefore, the ink ejection force when ejecting ink droplets from the nozzles is not uniform and this can cause disparities in the ink ejection volume and the ink ejection speed, thus leading to the appearance of differences in the sizes and positions of the dots formed on the recording medium and hence causing deterioration in image quality.
Furthermore, since the supply restrictors and nozzles have a small hole diameter, if foreign matter enters into the common liquid chamber, then blockages may occur in the supply restrictors or nozzles, possibly leading to ejection defects.